Process of producing gels for catalytic and adsorbent purposes



Patented Mar. 16, 1926.

UNITED, S TES l,577,186 PATENT OFFICE.

' ,wanrnn A. rararox, or nan'rmonn, MA YLAND.

r PROCESS OI PRODUCING GELS FOR CATALYTIC AND ADSOBBENT PURPOSES.

No Drawing.

To all whom it may concern:

Be it known that I, WALTER A. PATRICK, a citizen' of the United States, and residing at Baltimore city, State of Maryland, have invented certain new and useful Im rovements in Processes of Producing Ge s for Catalytic and Adsorbent Purposes, of which the following is a specification.

The present invention relates to adsorbent gels having chemically active or catalytic agents associated therewith. Y

In my Patent No. 1,297,724 I have dis-.

other substances.

The present invention comprehends gels of hard stable porous structure having ultra-' microscopic pores and also having associated therewith one or more members of the class of catalyzers containing metallic elements. I

From a chemical standpoint it is very des'irable to have certain substances in a physical structure similar to that of porous gels such as the silica gel described in the aforesaid patent. Silica is an inert substance chemically, and for this reason is admirably suited for adsorbing and recovering gases and vapors, provided of course that'it is given the pro er structure. On the other hand, other su stances, such as certain metallic oxides and metals are known to possess desirable chemical and catalytic properties. If these metalsand metallic oxides can be obtained with a structure similar to that of the gel described in the patent the above found necessary to allow the silicic acid to gen per liter.

Application filed February 28, 1920. Serial No. 862,138.

set to a hydrogel in a medium of certain definlte acid concentration in order to insure a gel of the proper structure. .The concentratlon of the acid is from about threetenths to nine-tenths gram ions of hydrogen per liter, the preferred concentration being about five-tenths gram-ions of hydro- The present invention utilizes hydrolysis of metallic salts to secure the proper acid concentration for the setting of the colloidal s1l1c1c acid. For example, if a solution of water glass of the proper concentration be m xed, with a solution of ferric chloride, the mixture will set to a hydrogel, which can be washed free of chlorides with substantlally no loss of iron, and the resulting hydrogel when dried as described in m patent, is found to consist of a mixture of silica and ferric oxide, together with .the usual quantity of water. Wide variation of the ratio of ferric oxide to silica may be ob tained by proper selection of the concentration and'volumes of water glass and ferric chloride solutions. The resulting gel adsorbes gases and vapors, with which it does not interact chemically, to the same degree as the plain silica gel of the patent. On the other hand, the addition of the ferric oxide increases theipower of the gel for adsorption of ases and vapors with which it may chemica ly combine. The iron oxide also adds catalytic properties to the gel. For example, the reaction between sulphur dioxide and oxygen is markedly catalyzed by the mixture of Fe O and SiO while the silica gel itself is without effect on the velocity of the above reaction.

This invention is in no wise limited to the above example, for it is possible to secure a great number of mixtures of metallic oxides with silica and similar substances by the application of the above principle. Thus aluminum oxide may be obtained intermixed with silica possessing a gel structure, providing proper solutions of aluminum chloride and water glass of the thereby completing the hydrolysis.

It is also possible to prepare gels of metallic salts that are not as easily hydrolyzed in water as the above, it being found that upon setting of the hydrogel, it is possible to wash the material free of the acid radical,

action has been explained by F. G. Donnan in his papers on Membrane permeability, published in volume 2 of System of Phys1' cal Chemistry by W. C. Mclaewis, page 275. For example, if a mixtureof copper chloride, water glass and hydrochloric acid be prepared ofsuch a nature that the whole will'set to a hydrogel, it is found that it is possible to entirely free the mixture of chlorides by washing without loss of much copper. The loss of copper in the washing depends upon the amount of acid used in the original mixture.

By the. application of this principle, which in the end amounts to the same thing as in the previously cited cases, it is possible to prepare. gels having one or more of the heavy metallic oxides mixed with silica or similar substances. In the first mentioned examples, the necessary acid was derived from the hydrolysis of the strongly hydrolyzed salts of heavy metals, e. g. A161,, FeCl etc., while in the latter example the acid was supplied as such.

It is easily possible to reduce a. mixture of certain of these oxides to a metallic state, and in this wa obtain a mixture of silica and finely divi ed metal, the whole possessing a structure analogous to silica gel. For example, the following gels comprising silica and a finely divided metal have been prepared, by reducing the corresponding metallic oxide gels with hydrogen at a low temperature Fe-l-SiG Cu-i-SiO, Ni-J-SiO This are mixed. According to the second method described herein, a silicate solution, acid solution, and a solution of a salt of a heavy metal are mixed. If improper proportions are taken a precipitate will result and the product of the present invention not' be ob tained. On the other hand, if the proper proportions and quantities are taken, the mixture gradually hardens into a hydrogel. This hydrogel by washing and drying is converted into the highly porous gel of the present invention. The precipitate mentioned above after being washed and dried may be the same chemically as the gel, but it does not have the same porous structure. The gel has muchfiner pores than the dried precipitate, and consequently the internal surface of the gel is many times as extensive as the internal surface of the dried precipitate. It is because of this extensive surface that these gels are so active catalytically. In preparing the gels, the liquid after mixing should have an acid concentration-of.

three-tenths to nine-tenths gram ions of according to the present invention it is possible to obtain hard adsorbent gels including a metal or metals or one or more metallic oxides, this mixture being obtained from a metallic salt and a silicate. Furthermore it will be observed that while silica is a chemically inert substance, the metals and metallic oxides which are incorporated in the gel according to this invention are chemically active as compared to silica and also possess catalytic properties.

The term gel as used in the specification and claims designates a hard porous material having a porous structure similar to that ofthe gel obtained by the process described in Patent No. 1,297,724.

The term metal as used iii the claims is not intended to include silicon and the term metal bearing material is used to designate a metal by itself as well as compounds thereof.

It is to be distinctly understood that any equivalent substance may be substituted for the sodium silicate and although the silicate has been referred to throughout the specification in connection with the preparation of the gel, this is merely illustrative of the class of substances that can be used to obtain the porous catalytic product of this invention.

The present application claims onlyone of the above processes for producing gels for catalytic and adsorbent purposes. The other process disclosed herein is claimed in my co-pending application Serial No.

715,731, filed May 24, 1924, which is a division ofthis case. The product disclosed herein is claimed in my co-pending applica--' tion Serial No. 715,727, filed May 24, 1924, which is also a division of this case.

Having thus described the invention what is claimed as new and desired to be secured by Letters Patent is:

1. In the process of preparing a hard porous gel impregnated with a catalytic agent, the step of mixing with stirring solutions of a readily hydrolizable salt of a heavy metal and a substance which will react with the acid resulting from the hydrolysis of the salt to produce a colloidal solution which will set to a hydro gel without removal of the excess acid or salt.

2. The process of preparing a hard porous gel impregnated with at least one -metallic oxide consisting in mixing, with stirring, solutions of a readily hydrolizable salt of said metal and a substance which will react with the acid resulting from the hydrolysis to produce a colloidal solution which Will set to a hydrogel, Washing out the excess acid and salt and drying the resulting product.

3. The process of preparing a hard porous gel impregnated with a catalytic agent, consisting in mixing with stirring solutions of a readily hydrolizable salt of a heavy metal and water glass to produce a colloidal solution which will set to a hydrogel, washing out the excess acid and salt and drying the resulting product.

4. The method of preparing a hard porous gel consisting in mixing with stirring solutions of a readily hydrolizable salt of a heavy metal and a substance which will react with the acid resulting from the hydrolysis or the salt to produce a colloidal solution, said salt and substance being in such proportions that neither gelatinization nor precipitation occurs at once, but after some time the entire body of liquid hardens into a hydrogel, washing the hydrogel thus formed and drying.

In testimony whereof I afiix my signature.

IVALTER A. PATRICK. 

